The present invention relates to devices for elevating liquids, in which liquid elevates in a pipe under the action of a pressure difference which is smaller than a pressure difference of a solid liquid column with a height equal to a height of elevation.
Devices of the above mentioned type (air-lifts) are known in the art. In the known devices a part of the liquid column in the pipe is replaced by gas gaps or plugs, preferably air gaps or plugs (bubbles). Such devices are disclosed in U.S. Pat. Nos. 532,699; 556,436; 566, 987; 580, 540; 597,023; 1, 154,745; 1, 343, 963; 1,741, 571; 4, 513, 887; 4, 519,749, British Pat. No. 2, 097, 485 and my U.S. Patent Application Ser. Nos. 700, 908 and 700, 961. The disadvantage of the above devices is that the pipe cannot exceed a certain diameter which is required for forming of stable liquid portions separated by gas portions, for a given material of the pipe and at a given temperature. Meniscuses which are formed at the upper and lower border of each liquid portion must not be destroyed under the action of weight of the liquid portions and loads caused by their movement along the pipe. For example, for providing stable water portions separated by gas portions in a glass pipe at the temperature of 20.degree. C., the inner diameter of the pipe must be lower than 4 mm, and for gasoline--not more than 3 mm.
U.S. Pat. No. 4,527,956 discloses a pipe for elevating liquids, which can have a greater diameter. However, it has a complicated construction, is expensive, has a great weight, offers high resistance to liquid flow, and requires high maintenance expenses.